This invention relates to sewer trap priming valves, i.e. to valves for use in charging water into sewer line water traps to prevent the escape of sewer gas.
Under normal conditions, the level of the water in sewer line traps decreases through evaporation by about one-eighth inch for each twenty-four hours. Accordingly, most municipal plumbing and sanitary codes require that means be provided for supplying water to the traps automatically or periodically to assure that the trap water level will be sufficiently high to render the trap operative and functional at all times.
To meet this requirement, it is usual to connect the trap to the house line through a priming valve which is actuated by variations in pressure in the house line and acts to charge the trap with water upon each fluctuation of pressure in the house line.
Several difficulties attend the use of the conventional sewer trap priming valves.
Most, if not all of them, require adjustment to line pressure in order to function properly. Since the valves are required to operate unattended over a long period of time, their moving parts are subject to corrosion and failure. Many are spring actuated and fail because of spring failure.
It is the general purpose of the present invention to provide a priming valve for sewer line traps which does not require special adjustment for line pressure; which dispenses a uniform amount of water in each of its operations; which maintains a proper level in the sewer line trap at all times; which discharges a metered amount of water with each operation; which will not flow continuously while the line comes back to pressure; which prevents back flow from trap to water line; and which is simple in construction, easily installed in diverse plumbing situations, and economical in operation.
Generally stated, the sewer line trap valve of our invention comprises a case having a bore longitudinally therethrough and means for connecting the case in series flow in a pressurized water line containing water under variable pressure.
A hollow shaft is mounted in the case and extends from the downstream portion toward the upstream portion thereof. A piston is slidably mounted on the shaft and divides the bore of the case into a downstream air chamber and an upstream water chamber.
Floating seal means is mounted within the water chamber upstream of the piston and hollow shaft. Both floating seal means and piston are retracted by water pressure from the water line when a condition of high pressure prevails therein, thereby compressing the air in the air chamber, and advanced by air pressure from the air chamber when a condition of low pressure prevails in the water line. In its retracted position the seal means connects the water line to the water chamber while sealing off the hollow shaft. This charges the water chamber with water and compresses the air in the air chamber.
In its advanced position, the floating seal seals off the water line from the water chamber and connects the water chamber with the hollow shaft. Upon concurrent advancement of the piston, the water content of the water chamber is discharged into the trap. Upon increase of the water pressure in the water line to its normal value, the seal is shifted to its advanced position, charging the valve with water and compressing the air in the air chamber, ready for another cycle of operation.